Two-step electrodeposition preparation method of nickel-cobalt sulfide and nickel-cobalt double hydroxide heterojunction self-supporting electrode

Abstract

The invention belongs to the field of supercapacitor electrode material preparation, and particularly relates to a two-step electrodeposition preparation method of a nickel-cobalt sulfide and nickel-cobalt double hydroxide heterojunction self-supporting electrode. The method comprises the following steps: (1) taking a solution prepared from nickel salt, cobalt salt and thiourea as a first electrolyte, and depositing nickel-cobalt sulfide on a conductive substrate by adopting a constant potential deposition method; and (2) taking a solution prepared from nickel salt and cobalt salt as a second electrolyte, and performing in-situ deposition of nickel-cobalt double hydroxide on the surface of the nickel-cobalt sulfide by adopting a constant potential deposition method to obtain the nickel-cobalt sulfide and nickel-cobalt double hydroxide heterojunction self-supporting electrode. The problems that an existing single-phase nickel-cobalt sulfide self-supporting electrode is low in specific capacitance; a single-phase nickel-cobalt double hydroxide self-supporting electrode is poor in multiplying power and cycle performance; and the preparation process of the existing super capacitor heterojunction composite self-supporting electrode is generally complicated.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrode material preparation, specifically relating to a two-step electrodeposition method for preparing a nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode. Background Technology

[0002] With global climate change and ever-increasing energy demand, fossil fuels, represented by coal, oil, and natural gas, face problems such as limited reserves, environmental pollution, and the greenhouse effect, and their proportion in the future energy structure will gradually decline. New energy storage devices, such as lithium-ion batteries, sodium-ion batteries, supercapacitors, solar cells, and fuel cells, will gradually replace the former and become the new favorites in the energy storage market. Lithium-ion batteries have high energy density but poor rate performance and cycle life, and also pose safety risks. Solar cells have large energy storage capacity and are easy to deploy, but their use is greatly affected by season, weather, and region. Fuel cells, while possessing considerable energy density, have a complex structure and are not portable. Compared to the aforementioned new energy devices, supercapacitors have advantages such as high power density, long cycle life, and portability, and have broad application prospects in the future energy market.

[0003] However, the energy density of supercapacitors is significantly lower than that of lithium-ion batteries, resulting in insufficient battery life when used alone, which greatly limits their development. Therefore, improving energy density has become a key issue in overcoming the bottleneck in the development of supercapacitors. The formula for calculating the energy density of a supercapacitor is E=1 / 2CV. 2 It is known that there are two ways to improve the energy density of a device: one is to increase the specific capacitance of the device, and the other is to widen the operating voltage window of the device. Regarding improving the specific capacitance of the device, the development of high specific capacitance cathode materials has received widespread attention from researchers. Among the many cathode materials for supercapacitors, nickel-cobalt sulfides and nickel-cobalt double hydroxides have attracted considerable attention due to their high theoretical specific capacitance. However, the actual specific capacitance of electrode materials is affected by factors such as their conductivity, specific surface area, and utilization rate of active materials, and is often lower than their theoretical value under actual operating conditions. Furthermore, in the traditional electrode fabrication process using a blade coating method, conductive agents and binders are often added to improve the conductivity and stability of the electrode, which further reduces the utilization rate of the active material, leading to a further decrease in the electrode's specific capacitance. To address this drawback, the current main approach is to use hydrothermal or electrodeposition methods to deposit the active material in situ onto a conductive substrate to construct a self-supporting electrode. This not only saves electrode fabrication time but also avoids the use of inert additives, effectively improving the utilization rate of the active material. On the other hand, constructing heterojunction composite materials from two materials with different compositions and structures can simultaneously build an interface-built electric field by controlling the electronic structure of the heterojunction interface, thereby improving the interface electron and ion transport dynamics and enhancing the power density and cycle performance of the electrode material.

[0004] In addition, patents have reported methods for preparing nickel-cobalt bimetallic sulfide heterostructure electrocatalysts with self-supporting nickel foam via a two-step solvothermal method, as well as methods for preparing multidimensional nickel-cobalt-based sulfide heterojunction electrocatalytic composite materials. These patents further confirm the feasibility of preparing heterojunction composite materials. Nevertheless, there are currently few reports on the preparation of nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrodes with nickel-cobalt sulfide as the core layer and nickel-cobalt double hydroxide as the shell layer. Moreover, the preparation of currently reported heterojunction composite electrodes with nickel-cobalt sulfide as the core layer involves at least one hydrothermal or solvothermal process. Compared with hydrothermal methods, electrodeposition offers numerous advantages such as shorter processing time, lower energy consumption, easier parameter adjustment, safer operation, and environmental friendliness, and is widely used in the preparation of self-supporting electrodes.

[0005] This invention utilizes the convenience of electrodeposition to rapidly prepare a heterojunction composite self-supporting electrode with nickel-cobalt sulfide as the core layer and nickel-cobalt double hydroxide as the shell layer. It fully leverages the high conductivity and high specific capacitance of nickel-cobalt sulfide, as well as the tunable composition and high specific capacitance of nickel-cobalt double hydroxide, to prepare a supercapacitor self-supporting electrode that combines high specific capacitance, high rate performance, and long cycle life. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a two-step electrodeposition method for preparing nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrodes. The method aims to solve the following problems: the specific capacitance of current single-phase nickel-cobalt sulfide self-supporting electrodes is low, the rate capability and cycle performance of single-phase nickel-cobalt double hydroxide self-supporting electrodes are poor, and the existing supercapacitor heterojunction composite self-supporting electrode preparation process is complex.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A two-step electrodeposition method for preparing a nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode, characterized by comprising the following steps: (1) Using a solution prepared with nickel salt, cobalt salt and thiourea as the first electrolyte, nickel cobalt sulfide was deposited on a conductive substrate by constant potential deposition method; (2) Using a solution prepared with nickel salt and cobalt salt as the second electrolyte, nickel cobalt double hydroxide is deposited in situ on the surface of nickel cobalt sulfide by constant potential deposition method to obtain the nickel cobalt sulfide@nickel cobalt double hydroxide heterojunction self-supporting electrode.

[0008] Furthermore, step (1) specifically includes: S1. Prepare the first electrolyte solution by dissolving nickel salt, cobalt salt and thiourea in deionized water; S2. Using a conductive substrate as the working electrode and the first electrolyte solution as the electrolyte solution, nickel-cobalt sulfide is deposited on the conductive substrate by a constant potential deposition method. Step (2) specifically includes: S3. Prepare the second electrolyte solution by dissolving nickel salt and cobalt salt in deionized water; S4. Using the electrode obtained after deposition in step S2 as the working electrode and the second electrolyte solution as the electrolyte solution, nickel cobalt double hydroxide is deposited in situ on the surface of the nickel cobalt sulfide using a constant potential deposition method to obtain the nickel cobalt sulfide@nickel cobalt double hydroxide heterojunction self-supporting electrode.

[0009] Furthermore, the nickel salt is selected from any one of nickel nitrate, nickel sulfate, nickel chloride, and nickel acetate; the cobalt salt is selected from any one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt acetate.

[0010] Furthermore, in step S1, the molar ratio of nickel salt, cobalt salt, and thiourea is 1:2:100~200.

[0011] Further, in step S1, the concentration of nickel salt is 0.005~0.02 mol / L, the concentration of cobalt salt is 0.01~0.04 mol / L, and the concentration of thiourea is 0.5~4.0 mol / L.

[0012] Furthermore, in step S3, the molar ratio of nickel salt to cobalt salt is 1:2 to 2:1.

[0013] Further, in step S3, the concentration of nickel salt is 0.005~0.02 mol / L, and the concentration of cobalt salt is 0.005~0.04 mol / L.

[0014] Furthermore, the conductive substrate is selected from any one of nickel foam, carbon cloth, and carbon paper.

[0015] Furthermore, in steps S2 and S4, a three-electrode system is used for constant potential deposition, wherein the counter electrode is a platinum sheet electrode and the reference electrode is a silver / silver chloride electrode; the process parameters for constant potential deposition are: deposition potential of -1.2 ~ -0.9 V, deposition time of 450 ~ 1800 s, and deposition temperature of 20 ~ 60℃.

[0016] This invention employs an electrodeposition method to construct a nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode in situ, which has the following beneficial effects: (1) Compared with the traditional hydrothermal / solventricular method, the electrodeposition method has significant advantages such as short time consumption, low energy consumption, safety and environmental protection, and easy control of process parameters, which is more conducive to industrial production.

[0017] (2) The self-supporting electrode prepared does not require the addition of conductive agents, binders and other polymer inert additives, which greatly reduces the electrode preparation cost and effectively avoids the dilution effect of "dead mass" on capacity, thereby significantly improving the utilization rate of active materials and helping to achieve higher specific capacitance.

[0018] (3) By constructing a nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction, a built-in electric field can be formed at the interface of the two components and the interface electronic structure can be optimized. This synergistic effect can effectively improve the transport dynamics of electrons and ions, and endow the electrode material with better rate performance and cycle stability.

[0019] (4) The nanoporous structure prepared by electrodeposition has a high specific surface area, which not only facilitates the full penetration of electrolyte and exposure of active sites, but also shortens the transport path of ions / electrons in the bulk phase of the material, thereby further enhancing the electrode reaction kinetics and improving the overall electrochemical performance.

[0020] (5) The carbon cloth and nickel foam substrates preferred in this invention have both high conductivity and good flexibility, and can be directly used to assemble flexible supercapacitors, which greatly broadens the application prospects of electrode materials in wearable and portable electronic devices.

[0021] In summary, the nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode obtained by this invention has high specific capacitance, excellent rate performance and long cycle life, and good flexibility, showing broad application potential. Attached Figure Description

[0022] Figure 1 The image shows a scanning electron microscope (SEM) image of the nickel-cobalt sulfide@nickel-cobalt double hydroxide / nickel foam (NCS@NCOH / NF) heterojunction self-supporting electrode prepared in Example 1 of this invention, and a comparison of its electrochemical performance with that of a control electrode.

[0023] in, Figure 1 a is a SEM image of the NCS@NCOH / NF electrode (the inset shows the full image); Figure 1 b is a comparison of the constant current charge-discharge curves of nickel cobalt sulfide / nickel foam (NCS / NF), nickel cobalt double hydroxide / nickel foam (NCOH / NF), and NCS@NCOH / NF electrodes prepared under the same conditions; Figure 1 c is a comparison chart of the rate performance of the three types of electrodes mentioned above; Figure 1 d is a comparison of the cycle performance of the three types of electrodes mentioned above.

[0024] Figure 2 These are morphological and electrochemical performance diagrams of the nickel-cobalt sulfide@nickel-cobalt double hydroxide / carbon cloth (NCS@NCOH / CC) heterojunction self-supporting electrode prepared in Example 2 of this invention.

[0025] in, Figure 2 a and Figure 2 b shows the SEM images of the NCS@NCOH / CC electrode at different magnifications; Figure 2 c is a comparison of the constant current charge-discharge curves of NCS / CC, NCOH / CC and NCS@NCOH / CC electrodes prepared under the same conditions; Figure 2 d is a comparison of the cycle performance of the three types of electrodes mentioned above.

[0026] Figure 3 These are the morphology and comprehensive electrochemical performance diagrams of the nickel-cobalt sulfide@nickel-cobalt double hydroxide / carbon cloth self-supporting electrode prepared in Example 3 of this invention.

[0027] in, Figure 3 a, Figure 3 b and Figure 3 c shows the SEM images of the electrode at different magnifications; Figure 3 d represents the constant current charge-discharge curve of the electrode; Figure 3 e represents the rate performance of the electrode; Figure 3 f is the cycle performance diagram of this electrode.

[0028] Figure 4 These are the morphology and comprehensive electrochemical performance diagrams of the nickel-cobalt sulfide@nickel-cobalt double hydroxide / carbon cloth self-supporting electrode prepared in Example 4 of this invention.

[0029] in, Figure 4 a, Figure 4 b and Figure 4 c shows the SEM images of the electrode at different magnifications; Figure 4 d represents the constant current charge-discharge curve of the electrode; Figure 4 e represents the rate performance of the electrode; Figure 4 f is the cycle performance diagram of this electrode. Detailed Implementation

[0030] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0032] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0033] In the following embodiments, the specific capacitance of the electrode material is calculated using the current-time curve integration method. The calculation formula is:

[0034] In the formula, Cs is the specific capacitance of the electrode material, in F g. -1 I represents current in A; u represents voltage in V; t1 and t2 represent the start and end times of charging and discharging, respectively, in seconds; m represents the mass of the electrode active material in g; Δu represents the voltage window in V.

[0035] Example 1 A method for preparing a nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode by electrodeposition on a nickel foam substrate and its electrochemical performance.

[0036] The specific steps for fabricating the above-mentioned heterojunction self-supporting electrode are as follows: The nickel foam was cut into sheets 3 cm long and 1 cm wide. The sheets were ultrasonically washed with anhydrous ethanol and deionized water for 20 min in sequence. Then, they were dried in a drying oven at 80 °C for 2 h. One sheet was taken out, weighed, and the mass was recorded as m1.

[0037] Using the aforementioned nickel foam as the working electrode, a platinum sheet as the auxiliary electrode, and a silver-silver chloride electrode as the reference electrode, containing 0.005 mol·L⁻¹ -1 NiSO4, 0.010 mol·L -1 CoSO4 and 1 mol·L -1 The thiourea solution was an electrolyte solution. The deposition potential was set to -1.0 V (vs. Ag / AgCl), the deposition time to be 900 s, and the deposition temperature to be 30 ℃. After deposition, the deposit was rinsed several times with deionized water, placed in a drying oven and dried at 80 ℃ for 5 h. The deposit was then weighed and recorded as m2. The mass of the nickel-cobalt sulfide was then m2-m1.

[0038] Using nickel foam with deposited nickel-cobalt sulfides as the working electrode, a platinum sheet as the auxiliary electrode, and a silver-silver chloride electrode as the reference electrode, a solution containing 0.005 mol·L⁻¹ was used. -1 NiSO4 and 0.010 mol·L -1 The Co(NO3)2 solution was used as the electrolyte solution. The deposition potential was set to -1.0 V (vs. Ag / AgCl), the deposition time was 900 s, and the deposition temperature was 30 ℃. After deposition, the deposit was rinsed several times with deionized water and then dried in a drying oven at 80 ℃ for 5 h. The deposit was then weighed and recorded as m3. The mass of the nickel-cobalt double hydroxide is m3-m2, and the total mass of the active material is m3-m1.

[0039] like Figure 1 Figure a shows the SEM image of the nickel-cobalt sulfide@nickel-cobalt double hydroxide self-supporting electrode prepared in this embodiment. As can be seen from the image, the surface of the nickel foam is covered by interwoven nanosheets, demonstrating good deposition performance. The large pores between the nanosheets facilitate electrolyte wetting and accelerate electrode reaction kinetics. Furthermore, the nanoscale morphology shortens the transport distance of electrons and ions in the deposited phase, further accelerating the electrode reaction rate. Simultaneously, the nanoscale morphology increases the reaction area, which is beneficial for improving the specific capacitance of the material. To illustrate the advantages of the electrochemical performance of the heterojunction self-supporting electrode, Figure 1 b provides self-supporting electrodes of NCS / NF, NCOH / NF and NCS@NCOH / NF prepared under the same conditions at 5 A·g. -1 The initial constant-current charge-discharge curves at the current density are shown in the figure. As can be seen from the figure, the charge-discharge curves of the three electrodes have similar shapes, and all show a pair of obvious charge-discharge voltage plateaus, indicating that this type of material has pseudocapacitive characteristics. Figure 1 c and Figure 1 Figure d shows a comparison of the rate performance and cycle performance of each electrode. As can be seen from the figure, the NCS@NCOH / NF heterojunction self-supported electrode exhibits better electrochemical performance compared to the single-phase NCS / NF and NCOH / NF self-supported electrodes. Specifically, at 5 A·g... -1 The discharge specific capacitances of NCS / NF, NCOH / NF, and NCS@NCOH / NF are 888.9, 669.8, and 769.3 F·g, respectively. -1 After 5000 cycles at this current density, the capacitance retention rates were 69.7%, 53.2%, and 82.9%, respectively. The current density was increased to 20 A·g. -1 The discharge specific capacitances of each electrode are 768.5, 489.0, and 684.4 F·g, respectively. -1 .

[0040] Example 2 A nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode prepared by electrodeposition on a carbon cloth substrate and its electrochemical properties.

[0041] The specific steps for fabricating the self-supporting electrode described above are as follows: The carbon cloth was cut into pieces 3 cm long and 1 cm wide. It was then ultrasonically washed with anhydrous ethanol and deionized water for 20 min in sequence. After that, it was placed in a drying oven and dried at 80 ℃ for 2 h. One piece was taken out, weighed, and the mass was recorded as m4.

[0042] Using the aforementioned carbon cloth as the working electrode, a platinum sheet as the auxiliary electrode, and a silver chloride electrode as the reference electrode, containing 0.005 mol·L⁻¹ -1 NiSO4, 0.010 mol·L -1CoSO4 and 1 mol·L -1 The thiourea solution was an electrolyte solution. The deposition potential was set to -1.0 V (vs. Ag / AgCl), the deposition time to be 900 s, and the deposition temperature to be 30 ℃. After deposition, the deposit was rinsed several times with deionized water, placed in a drying oven and dried at 80 ℃ for 5 h. The deposit was then weighed and recorded as m5. Therefore, the mass of the nickel-cobalt sulfide is m5-m4.

[0043] A carbon cloth deposited with nickel-cobalt sulfides was used as the working electrode, a platinum sheet as the auxiliary electrode, and a silver-silver chloride electrode as the reference electrode, containing 0.005 mol·L⁻¹ -1 NiSO4 and 0.010 mol·L -1 The Co(NO3)2 solution was used as the electrolyte solution. The deposition potential was set to -1.0 V (vs. Ag / AgCl), the deposition time was 900 s, and the deposition temperature was 30 ℃. After deposition, the deposit was rinsed several times with deionized water and then dried in a drying oven at 80 ℃ for 5 h. The deposit was then weighed and recorded as m6. Therefore, the mass of the nickel-cobalt double hydroxide is m6-m5, and the total mass of the active material is m6-m4.

[0044] like Figure 2 Figure ab shows the SEM images of the NCS@NCOH / CC self-supporting electrode prepared in this embodiment. As can be seen from the images, the morphology of the deposit is roughly the same as that observed in Example 1, consisting of interwoven nanosheets. This material tightly wraps and binds the carbon cloth fibers, ensuring that the material does not detach during charge-discharge cycles, thus contributing to better cycle stability. Furthermore, the abundant surface area of ​​the deposit is conducive to electrode reactions, enhancing the electrode's charge storage capacity. Simultaneously, the nanoscale material facilitates bulk ion and electron transport, thereby enhancing electrode reaction kinetics. Figure 2 c and Figure 2 Figure d shows a comparison of the constant current charge-discharge curves and cycle performance of NCS / CC, NCOH / CC, and NCS@NCOH / CC self-supporting electrodes prepared under the same conditions. Specifically, the current density is 5 A·g. -1 The discharge specific capacitance of the NCS@NCOH / CC electrode is 2001.6 F·g. -1 Higher than NCS / CC (954.7 F·g) -1 ) and NCOH / CC (1375.2 F·g -1 After 5000 cycles, the NCS@NCOH / CC electrode retained 55.3% of its initial capacity, slightly lower than that of NCS / CC (68.1%).

[0045] Example 3 A nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode prepared by electrodeposition on a carbon cloth substrate and its electrochemical properties.

[0046] The specific steps for fabricating the self-supporting electrode described above are as follows: The carbon cloth was cut into pieces 3 cm long and 1 cm wide. It was then ultrasonically washed with anhydrous ethanol and deionized water for 20 min in sequence. After that, it was placed in a drying oven and dried at 80 °C for 2 h. One piece was taken out, weighed, and the mass was recorded as m7.

[0047] Using the aforementioned carbon cloth as the working electrode, a platinum sheet as the auxiliary electrode, and a silver chloride electrode as the reference electrode, containing 0.005 mol·L⁻¹ -1 NiSO4, 0.010 mol·L -1 CoSO4 and 0.5 mol·L -1 The thiourea solution was an electrolyte solution. The deposition potential was set to -1.0 V (vs. Ag / AgCl), the deposition time to be 900 s, and the deposition temperature to be 30 ℃. After deposition, the deposit was rinsed several times with deionized water, placed in a drying oven and dried at 80 ℃ for 5 h. The deposit was then weighed and recorded as m8. Therefore, the mass of the nickel-cobalt sulfide is m8-m7.

[0048] A carbon cloth deposited with nickel-cobalt sulfides was used as the working electrode, a platinum sheet as the auxiliary electrode, and a silver-silver chloride electrode as the reference electrode, containing 0.005 mol·L⁻¹ -1 NiSO4 and 0.010 mol·L -1 The Co(NO3)2 solution was used as the electrolyte solution. The deposition potential was set to -1.0 V (vs. Ag / AgCl), the deposition time was 900 s, and the deposition temperature was 30 ℃. After deposition, the deposit was rinsed several times with deionized water and then dried in a drying oven at 80 ℃ for 5 h. The deposit was then weighed and recorded as m9. The mass of the nickel-cobalt double hydroxide is m9-m8, and the total mass of the active material is m9-m7.

[0049] like Figure 3 As shown in Figure ac, this is a SEM image of the nickel-cobalt sulfide@nickel-cobalt double hydroxide / carbon cloth self-supporting electrode prepared in this embodiment. As can be seen from the figure, the deposit still maintains the nanosheet morphology and is rich in pores. Figure 3 d represents the electrode at 5 A·g -1 The constant current charge-discharge curve under these conditions shows a clear charge-discharge plateau, and the discharge specific capacitance is 1284.6 F·g. -1 . Figure 3 e represents the rate performance curve of the electrode at 1, 2, 3, 5, 10, 20, and 50 A·g. -1The discharge specific capacitances at the following values ​​were 1342.2, 1317.9, 1305.4, 1284.6, 1259.4, 1149.9, and 639.2 F·g, respectively. -1 It exhibits excellent rate performance. Figure 3 f is the cycle performance graph of this electrode. As can be seen from the graph, at 10 A·g... -1 After 10,000 cycles, the post-discharge specific capacitance can be maintained at 71.3%, which is the best level in the current embodiment.

[0050] Example 4 A nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode prepared by electrodeposition on a carbon cloth substrate and its electrochemical properties.

[0051] The specific steps for fabricating the self-supporting electrode described above are as follows: The carbon cloth was cut into pieces 3 cm long and 1 cm wide. It was then ultrasonically washed sequentially with anhydrous ethanol and deionized water for 20 min each. Afterward, it was dried in a drying oven at 80 ℃ for 2 h. One piece was taken out, weighed, and its mass recorded as m. 10 .

[0052] Using the aforementioned carbon cloth as the working electrode, a platinum sheet as the auxiliary electrode, and a silver chloride electrode as the reference electrode, containing 0.005 mol·L⁻¹ -1 NiSO4, 0.010 mol·L -1 CoSO4 and 0.5 mol·L -1 The thiourea solution was used as an electrolyte solution. The deposition potential was set to -1.0 V (vs. Ag / AgCl), the deposition time to be 900 s, and the deposition temperature to be 30 ℃. After deposition, the deposit was rinsed several times with deionized water, placed in a drying oven and dried at 80 ℃ for 5 h. The deposit was then removed, weighed, and its mass recorded as m. 11 The mass of nickel-cobalt sulfide is m. 11 -m 10 .

[0053] A carbon cloth deposited with nickel-cobalt sulfides was used as the working electrode, a platinum sheet as the auxiliary electrode, and a silver-silver chloride electrode as the reference electrode, containing 0.010 mol·L⁻¹ -1 NiSO4 and 0.005 mol·L -1 The Co(NO3)2 solution was used as the electrolyte solution. The deposition potential was set to -1.0 V (vs. Ag / AgCl), the deposition time was 900 s, and the deposition temperature was 30 ℃. After deposition, the deposit was rinsed several times with deionized water, then placed in a drying oven and dried at 80 ℃ for 5 h. The deposit was then removed, weighed, and its mass was recorded as m. 12 The mass of nickel-cobalt double hydroxide is m. 12 -m 11The total mass of the active substances is m 12 -m 10 .

[0054] like Figure 4 As shown in Figure ac, this is a SEM image of the nickel-cobalt sulfide@nickel-cobalt double hydroxide / carbon cloth self-supporting electrode prepared in this embodiment. As can be seen from the figure, the deposit still maintains the nanosheet morphology and is rich in pores. Figure 4 d represents the electrode at 5 A·g -1 The constant current charge-discharge curve under the given conditions shows a clear charge-discharge plateau, with a discharge specific capacitance of 1333.7 F·g. -1 . Figure 4 e represents the rate performance curve of the electrode at 1, 2, 3, 5, 10, 20, and 50 A·g. -1 The discharge specific capacitances at the following values ​​were 1399.8, 1383.4, 1374.7, 1333.7, 1194.1, 1010.9, and 119.4 F·g, respectively. -1 , at 50 A·g -1 The capacity decreases significantly at lower speeds. It exhibits excellent rate performance. Figure 4 f is the cycle performance graph of this electrode. As can be seen from the graph, at 10 A·g... -1 After 10,000 cycles, the discharge specific capacitance can be maintained at 60.1%.

[0055] Comparative Example 1: Comparison of the process and performance of the method of this invention and the method reported in the literature To highlight the advantages of the two-step electrodeposition method described in this invention, a paper published in the journal Energy Advances that uses a three-step hydrothermal method to prepare nickel-cobalt-based heterojunction electrodes [1] was selected as a comparison object and systematically compared with the best embodiment of this invention. The results are summarized in Table 1.

[0056] References: [1]S. Wang, W. Jiang, J. Wu, H. Huang, P. Guo, X. Zhang, H. Gu, Q.Huang, Y. Hu, Engineering heterostructured nickel–cobalt sulfide@hydroxidenanoarrays with spontaneous and fast interfacial charge transfer for high-energy-density supercapacitors, Energy Advances, 1 (2022) 704-714. Table 1. Comparison of process and performance between the methods in the literature and the methods of this invention.

[0057] Comparative analysis: As shown in Table 1, compared with the three-step hydrothermal method using high temperature, high pressure, and time consumption in the comparative example, the two-step constant potential deposition method provided by this invention has significant advantages: (1) The preparation process is significantly simplified: The present invention simplifies the traditional multi-step hydrothermal method into a two-step room temperature and pressure electrodeposition process. The deposition time of a single step is only 15 minutes, and the total preparation time is greatly shortened from more than 14 hours to 30 minutes. Moreover, the deposition process is carried out at room temperature (30°C), which significantly reduces energy consumption. The process is green and environmentally friendly and more suitable for large-scale production.

[0058] (2) Excellent electrochemical performance: Although the active material loading of the electrode of this invention is approximately 1.0 mg cm⁻¹ -2 ) lower than the control group (8.1 mg cm -2 However, at higher current densities (10 A·g), -1 After undergoing a longer cycle test (10,000 cycles), the electrode still retains 71.3% of its initial capacitance, fully demonstrating the excellent long-cycle stability of the electrode under harsh high current density operating conditions. Meanwhile, the electrode of this invention maintains stability at 1~50 A·g. -1 It maintains a high specific capacitance over a wide current density range, exhibiting excellent rate performance.

[0059] In summary, this invention rapidly constructs a nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode under mild conditions using a two-step constant potential deposition method. While maintaining good electrochemical performance, it significantly simplifies the preparation process, shortens the preparation cycle, and reduces energy consumption, providing a highly promising technical solution for the low-cost, large-scale preparation of high-performance supercapacitor electrodes.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A two-step electrodeposition method for preparing a nickel-cobalt sulfide@nickel-cobalt double hydroxide heterojunction self-supporting electrode, characterized in that, Includes the following steps: (1) Using a solution prepared with nickel salt, cobalt salt and thiourea as the first electrolyte, nickel cobalt sulfide was deposited on a conductive substrate by constant potential deposition method; (2) Using a solution prepared with nickel salt and cobalt salt as the second electrolyte, nickel cobalt double hydroxide is deposited in situ on the surface of nickel cobalt sulfide by constant potential deposition method to obtain the nickel cobalt sulfide@nickel cobalt double hydroxide heterojunction self-supporting electrode.

2. The method as described in claim 1, characterized in that, Step (1) specifically includes: S1. Prepare the first electrolyte solution by dissolving nickel salt, cobalt salt and thiourea in deionized water; S2. Using a conductive substrate as the working electrode and the first electrolyte solution as the electrolyte solution, nickel-cobalt sulfide is deposited on the conductive substrate by a constant potential deposition method. Step (2) specifically includes: S3. Prepare the second electrolyte solution by dissolving nickel salt and cobalt salt in deionized water; S4. Using the electrode obtained after deposition in step S2 as the working electrode and the second electrolyte solution as the electrolyte solution, nickel cobalt double hydroxide is deposited in situ on the surface of the nickel cobalt sulfide using a constant potential deposition method to obtain the nickel cobalt sulfide@nickel cobalt double hydroxide heterojunction self-supporting electrode.

3. The method as described in claim 2, characterized in that: The nickel salt is selected from any one of nickel nitrate, nickel sulfate, nickel chloride, and nickel acetate; the cobalt salt is selected from any one of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt acetate.

4. The method as described in claim 2, characterized in that: In step S1, the molar ratio of nickel salt, cobalt salt and thiourea is 1:2:100~200.

5. The method as described in claim 2, characterized in that: In step S1, the concentration of nickel salt is 0.005~0.02 mol / L, the concentration of cobalt salt is 0.01~0.04 mol / L, and the concentration of thiourea is 0.5~4.0 mol / L.

6. The method as described in claim 2, characterized in that: In step S3, the molar ratio of nickel salt to cobalt salt is 1:2 to 2:

1.

7. The method as described in claim 2, characterized in that: In step S3, the concentration of nickel salt is 0.005~0.02 mol / L, and the concentration of cobalt salt is 0.005~0.04 mol / L.

8. The method as described in claim 2, characterized in that: The conductive substrate is selected from any one of nickel foam, carbon cloth, and carbon paper.

9. The method as described in claim 2, characterized in that: In steps S2 and S4, a three-electrode system is used for constant potential deposition, wherein the counter electrode is a platinum sheet electrode and the reference electrode is a silver / silver chloride electrode; the process parameters for constant potential deposition are: deposition potential of -1.2 ~ -0.9 V, deposition time of 450 ~ 1800 s, and deposition temperature of 20 ~ 60℃.

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